An herbal extract used in traditional Chinese medicine called Tripterygium wilfordii Hook F (TwHF) is “not inferior” to methotrexate for treating rheumatoid arthritis (RA), and causes few side effects, according to a study published recently online in of Annals of Rheumatic Disease.

Methotrexate, a disease-modifying antirheumatic drug (DMARD), is often used in the United States as an effective first-line therapy for treating RA. But it doesn’t work well, or well enough, for everyone. Those whose disease activity remains high while on methotrexate often start combination therapy by adding a second or third DMARD or a biologic drug.

In China, extracts made from the root of TwHF – also known as thunder god vine – are used to treat RA. The herb is traditionally prescribed to treat joint pain, fever, and localized swelling. Prior to this study, several smaller studies found TwHF to be effective for people with RA.

The new study comes from doctors at China’s Peking Union Medical College Hospital, in Bejing, who say they treat thousands of RA patients each year with a combination of methotrexate and TwHF. To prove its effectiveness, they conducted a randomized controlled trial in 207 RA patients.

Patients received either 12.5 milligrams (mg) of methotrexate once a week, 20 mg of TwHF three times a day, or both. After 12 weeks, those who weren’t seeing an adequate response were switched to the combination therapy.

After 24 weeks, patients who took TwHF alone improved no less than those who took methotrexate alone. (Because the study was designed as a “non-inferiority trial,” it can’t be said that the herb worked “as well as” methotrexate, only that it worked no worse than methotrexate.) Patients who took both saw the biggest improvement.

The outcomes were gauged in part by the ACR (American College of Rheumatology) 50 response. According to this measure, a treatment is considered successful if a patient has a 50 percent or greater improvement in several areas, including number of  tender and swollen joints, the patient’s self-assessment of pain and function, and indicators of inflammation levels in the blood, such as C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR or sed rate).

“The magnitude of the benefit in combination with methotrexate was somewhat unexpected and very gratifying,” says Peter E. Lipsky, MD, one of the study authors. “Previous work has demonstrated the beneficial effects of this treatment in RA as a stand-alone therapy. This trial is the first one to show the excellent benefit of this extract in combination with methotrexate.”

The herb contains “potent novel chemicals” that help with RA, says Dr. Lipsky. “Components of this extract have potent anti-inflammatory and immunoregulatory effects by inhibiting expression of specific genes encoding a number of mediators of inflammatory and immune activity.”

Rheumatologist David Pisetsky, MD, professor of medicine at Duke University, calls the study “interesting and very well done,” and says he doesn’t think the results are a big surprise. “This has been studied now for a quite a few years. Dr. Lipsky is an outstanding immunologist, and he’s done a lot of excellent basic science to show that there’s activity in [TwHF]. So the fact that it worked is quite consistent with what we know about agents in the herb.”